After I had sex, two weeks after that I got period. Aftr my period, 3 weeks after that I bought a pregnancy tube to test whether I am pregnant or not. But it says I'm not pregnant. But is there any chance I can get pregnant?

You had your period after your last sexual encounter, so it's unlikely that you are pregnant.

Can you get pregnant? Of course you can, unless you've had your tubes tied, or a hysterectomy, or there's a health issue that would make it impossible for you to bear children, you could get pregnant any time you have sex, even if protection is used.

But are you pregnant now? Unlikely since you had your period. Or did you have sex since your last period?